Piston



Jan. 30,1934. Q w, MARS 7' w 1,945,151

I PISTON I Original Filed June 1, 1931 429 35 1a 42 Z J0 J5 2] I I0 I I1 1 I Q .47

22/ g wff Patented Jan. 30, 1934 UNITED STATES PATENT OFFICE Originalapplication June 1, 1931, Serial No. 541,301. Divided and thisapplication June 6, 1932. Serial No. 615,633

9 Claims; (Cl. 309-34) The present invention relates to pistons, and isparticularly concerned with pistons of the type adapted to be employedin a cylinder for use in pumps, air compressors, hydraulic rams;

air hoists, air chucks, railway air brakes, automobile brakes, doorcheoks and myriad other uses.

One of the objects of the invention is the provision of an improvedcylinder and piston ar- 10 rangement in which the piston is adapted torun idle without excessive tension or wear on the packing devicesemployed with the piston.

Another object is the provision of an improved pistcin in which theexpansion of the packing devices is controlled and regulated by theamount of fluid pressure acting upon the piston, so that compensation ismade for the increased tendency to leak past the packings under highpressure.

Another object is the provision of a piston of the class described, inwhich all of the moving parts are suitably arranged to prevent leakageof any kind past the piston under low pressures or-high pressures, andwhich is adapted to maintain a. constant pressure without substantialleakage, for long periods of time.

Another object is the provision of a piston of the class described,which is adapted to prevent the building up of a pressure behind thepackings, such as might tend to offset the compensating action of thehigh fluid pressure in the cylinder.

Another object is the provision of an improved piston of the classdescribed, which is capable of long and continuous service withoutnecessity for repacking.

Another object is the provision of a high pressure packing which isparticularly adapted to be usedin hydraulic machinery under extremelyhigh pressures, and which will operate-eflicientlyunder such pressuresfor an extremely long life.

Another object is the provision of an improved piston which ispeculiarly adapted to be utilized as a hydraulic ram and which isadapted to maintain a fluid-tight joint for a long period 01' time underthe most adverse conditions.

The present application is a division of my parent application, SerialNo. 541,301, filed June 1, 1931, on pistons, and relates particularly toone of the embodiments disclosed in Fig. 4 of said parent application.

Other objects and advantages of the invention will be apparent from thefollowing description and from the accompanying drawing, in whichsimilar characters of reference indicate similar parts throughout theseveral views.

Referring to the single sheet of drawing:

Fig. 1 is a sectional view of a cylinder and a piston taken on a planepassing through the axis of the cylinder and piston;

Fig. 2 is an elevational view of the piston with the cylinder insection; and 1 Fig. 3 is a diagrammatic cross sectionalview takenthrough one of the packings, the packing seat, and the expander,employed in the present piston, showing the expanding action which takesplace in the packing.

Referring to Figs. 1 and 2, the packings which are utilized in thepresent improved piston preferably consist of closed rings or moldedleather members having a substantially V-shaped cross section, as shownin Fig. 3.

While theclosed leather rings are preferred for the reason that there isless possibility of leakage than where a split ring is employed, splitrings formed of strips of the same material of V-shaped cross section,with the ends of the strip in abutting relation, may also be utilizedwhere a plurality of packings are employed, and in such case the jointsin the respective rings are prefer-. ably staggered with respect to eachother. I

The packing rings, indicated by the numeral 10, may also be arranged inthe form of a helix, of which the separate turns constitute the variousrings, but in such case the expander and seat should be formed of ashape complementary to the ends of a helix of packing of this type, inorder that the expander and seat may come into engagement with thepacking about the full periphery of the piston.

The packing rings 10 are preferably provided with a pair offrusto-conical flanges 11 and 12 joined together at the apex 13 alongthe line of a circular iorme packing of substantially V shape. A helicalstrip of V-shaped packing may also be employed with expanders of thetype illustrated, provided the ends of the helix are beveled off verygradually to a sharp point so that there is no offset at the end of thehelix.

The edges 14 and 15 of the packing are preferably beveled to formsubstantially sharp edges or lips 16, 17, the edges 14 and 15 beingsubstantially cylindrical in shape and concentric with each other. Whenanumber of turns or rings of V- shaped-packing are employed, thepackings are nested ineach other, as shown in Fig. 1, the inside of eachlower packing engaging the outside of the next adjacent packing. Eachring of packing is thus supported by the adjacent rings of packing, andall of the rings are expanded together at the same time.

The packings are preferably actuated by a pair of members 18, 19, actingasthe expander packing.

The concave annular groove 20 is of less depth than the altitude of theV-shaped section of the ring, so that the member 19 initially engagesthe apex 13 of the packing and through the interengagement of thesuccessive layers of packing is adapted to support the apices inpredetermined position as the flanges are forced downward.

The expansion member 18 is preferably provided with a convex packingengag ng surface-21, which is of less height than the altitude of theV-shaped section of one of the packing rings, so that the convex surfaceof the metal expansion ring initially engages the lower inside edges 22,23 of the adjacent packing ring. Through the inter-engagement of thepacking ring 10 with the other packing rings, the upper expansion member18 is adapted to force outward all of the outer edges of the packingrings which are nested together.

Referring to Fig. 3, this is a diagrammatic illustration of theexpanding action of the members 18 and 19 on the packing rings, and,while a single packing ring is illustrated in Fig. 3 for the purpose ofclarity, the action is the same when a plurality of packing rings areemployed, and the packing rings are nested together, as shown in Fig. 1.

The full line illustration of the packing 10 shows the same in itsnormal position seated on the member 19, and before pressure is appliedthereto by the expanding member 18 to effect a relative movement of theexpansion members, such as the movement ofthe upper expansion ring inthe direction of the arrow, the apex 13 is forced toward the sharp edges16 and 17. Since the width of the flanges 11, 12 is greater than thespace between the opposite edges 14 and 15, the packing is expandededgewise to the position shown in the dotted lines in Fig. 3.

The concavely curved surface 20 of the seat 19 and the convexly curvedsurface 21 of the. expansion member. 18 are preferably such that whenthe packing is fully expanded the said expansion member and seat engageand reinforce the V-shaped leather packing to hold it in predeterminedposition and prevent the packing from any bending action under theinfluence of the frictional engagement between the packing and the wallof the piston. The rings are thus prevented from slithering back andforth where the packing is employed in a reciprocating member, butareadapted to take up the wear and maintain a fluid-tight joint at alltimes.

The packing is preferably arranged so that the pressure is greater onthe inside of the V-shaped packing than on the outside, that is, at thetop of Fig. 3 the greater pressure is applied so that the fluid pressuretends to force the sharp edges 16, 1'? into closer engagement with thewalls of the cylinder.

Referring to Figs. 1 and 2, the piston illustrated in these figures isprovided with V-shaped packings of the type just described, and anynumber of packings may be employed.

The cylinder 24 is provided with an inner cylindrlcal surface 25substantially complementary to the outer cylindrical surface 26 ofapiston 27. The piston 27 has its upper end 28 formed with a convexannular surface 20 similar to that of the seat 19, and it will beevident that the upper end of the piston constitutes the seat for thepackings.

The piston is provided with an axially extending bore 29 communicatingwitha concentrically located counterbore 30, and the end of the coun-'terbore 30 may be threadedas at 31 for receiving the threaded end 32 ofpiston rod 33, which may be provided with an annular flange 34 forengaging the end of the piston 27. The bore 29 in the'piston 27 slidablyreceives a plunger or rod 35 which movably supports the upper expansionmember 18 for engagement with a multiplicity of packings 10. The upperexpansion member 18 is provided with an annular convex surface 21previously described, and it is also preferably provided with aplurality of apertures 36 for providi communication between the interiorof the piston 25 and the space 37 below the expansion ring adjacentthepackings 10. The plunger 35 is preferably provided with a reducedthreaded upper end 38, thereby forming an. annular shoulder 39, and theupper expansion member may be provided with a bore 40 for receiving thereduced end 38 and. with a counterbore 41 for receiving the upperportion of the rod-35.

The nut 42 may be threaded on the upper end of the rod 35 to secure theexpansion member 18 in place, or in some forms of the invention othertypes of securing devices may be employed.

The lower end of the rod 35, in Fig. 1, is also 105 provided with a.reduced threaded portion 43, forming an annular shoulder 44, againstwhich may be seated a washer 45, which fits about the reduced portion 43and provides a seat 1 or a helical coil spring 46. The nut 47 on'thethreaded 110 end 43 secures the-washer in place against the annularshoulder 44, and the cotter-pin 48 assures the flxity of the nut 47, thecotter-pin passing through an aperture in the reduced end 43. A similarcotter-pin may be employed at the upper 115 end, if desired.

It will be observed that the expansion ring-18 initially engages theinside of the packing assembly at the points 22 ,and 23 while thesurface 20 initially engages the apex 13 of the lowermostpacking, andthe expansion member therefore tends to expand the packings 'l0,in Fig.1, exactly as described with respect to Fig. 3. a

The spring 46 is under initial compression and tends to draw the rod 35downward to urge the expansion member and seat toward each other,. andthe spring 46 constantly tends to effect expansion of the packings 10,to take up any wear and maintain a fluid-tight joint.

The pressure in the cylinder 24 above the piston 27 also tends to forcethe flanges 11 and 12 of the packing into closer engagement with thewalls of the cylinder, and it will be noted that the packing not onlyprovides a fluid-tight joint between the piston and the cylinder, butbetween the piston and the plunger rod 35. v

. The counte'rbore 30 is preferably placed in communication with theatmosphere by a conduit 49, which extends downward through the threadedplug 32, and piston. rod 33, and communicates .i with the atmosphere atthe point 50. Where pistons of the type described are used forcontinuous service or for the purpose of maintaining a pressure in thecylinder 24, a slight degree of leakage past the packings 10 may beexpected, and this leakage would pass down the bore 29 into thecounter-bore 30 and would otherwise build up in' thecounterbore 30 ifmeans were not provided, such as the conduit 49, for releasing thispressure. The building up of fluid pressure below the p'acking 10 or inthe counterbore 30 would render the .packing ineffective, and thereforethe piston is preferably provided with fluid pressure release means,such as conduit 49.

The packing rings in devices constructed according to the presentinvention may also consist of alternate rings of felt and leather of thesame shape, or occasional felt rings may be incorporated, the felt ringsbeing impregnated with oil or solid grease so that they are adapted tocon tinuously lubricate the packed joint, but the packing ringsthemselves are preferably constructed of the. best leather, treated withoils or greases adapted to withstand the acids, fluids, heat, and otheragencies to which the particular rings may be subjected.

The operation of the present piston will be evident from the descriptionof its construction and the functions of its parts previously described.

One of the most important features of the piston is the fact that anincrease of pressure on the pressure side of the piston tends to expandthe packings into firmer engagement with the walls 'of the cylinder andwith the parts of the piston which might otherwise leak, such as theplunger 35.-

This enables the piston to adjust its sealing action to the force orpressure which is placed upon'it, and the piston may run free or idlewithout any substantial wear on the packing because no great amount ofpressure is placed upon the piston while it is idling. As soon as thepiston starts: to do effective work, however, the increase in pressurein the cylinder increases the tendency of the packings to preventleakage.

It will thus be observed-that I have invented an improved form of pistonin which the sealing action of the packings is increased by the pressurein the cylinder in which the piston is mounted. The pressure not'onlyeffects an expansion of the packing at the outer surface of the piston,but of the packings surrounding it, and the present pistons are capableof maintaining high pressures without leakage for long periods of timewithout any necessity for repacking the pistons.

While I have illustrated a preferred embodiment of my invention, manymodifications may be made without departing from the spirit of theinvention, and I do not wish to be limitedto the precise details ofconstruction set forth, but desire to avail myself of all changes withinthe scope of the appended claims.

Having thus described my invention, what I .claim is new and desire tosecure by Letters Patent of the United States, is:

1. A hydraulic ram piston comprising a cylindrical body having a borepassing through the same, and having an annular concavely formed packingseat, a plunger mounted in said bore, a plurality of layers ofsubstantially V-shaped leather packings about the end of saidplunger,

7 and adapted to engage the wall of a cylinder in f which said piston ismounted, said packings hav ing the apex of one end packing in initialengage- L ment with the packing seat, and an expander carried by the endof said plunger 'and having a convex annular surface engaging the insideof the flanges of the other end packing adjacent its edges, theexpansion of said packings being increased responsive to increase offluid pressure on the piston plunger.

2. A hydraulic ram piston comprising a cylindrical body having a borepassing through the same, and having an annular concavely formed packingseat, a plunger mounted in said bore, a

plurality of layers of substantially v-shaped leather packings about theend of said plunger,

and adapted to engage the wall of a cylinder in which said piston ismounted, said packings having the apex of one end packing in initialengagement with the packing seat, an expander carried by the end of saidplunger and having a 'convex annular surfaceengaging the inside of theflanges of the other end packing adjacent its edges, the expansion ofsaid packings being increased responsive to increase of fluid pressureonthe piston plunger, 'and a spring carried by the other end of saidplunger and reacting against said plunger and said piston to drawsaidexpander against said packings.

3. A hydraulic ram piston comprising a cylindrical body having a borepassing through the same, and having an annular concavely formed packingseat, a plunger mounted in said bore, a plurality of layers ofsubstantially V-shaped leather packings about the end of said plunger,and adapted to engage the wall of a cylinder in which said piston ismounted, said packings having the apex of one end packing in initialengagement with the packing seat, an expander carried by the end of saidplunger and havin a convex annular surface engaging the inside of theflanges of the other end packing adjacent its edges, the expansion ofsaid packings being increased responsive to increase of fluid pressureon the piston plunger, a spring carried by the other end of said plungerand reacting against said plunger and said piston to draw said expanderagainst said packings, said piston having a counterbore surrounding saidspring, and a con- 11:, necting rod secured in said counterbore, saidcounterbore communicating with the atmosphere through a bleederconduitto prevent building up of pressure in said counterbore.

v 4. In a piston, the combination of a support- 115 ing body which isprovided with an upper concave annular surface, said body having anouter cylindrical surface and having an axial bore ex. tending into saidbody, said concave annular surface extending radially from said outercylindri- 120 cal surface to the edge of said bore, a plunger slidablymounted in said axial bore and carrying at its end an expansion memberhaving a lower convex annular surface, and a plurality' of packingscomprising flexible impermeable members,

each provided with a pair of frusto-conical flanges, said flanges ofeach packing being joined together along the line of a circle to form asubstantially V-shaped member having beveled edges, the outer edges ofsaid packings being adapted to engage the walls of a cylinder, and theinner walls of said packings engaging said plunger, whereby the jointbetween said plunger and said piston is sealed against leakage and saidplunger is actuated responsive to increased fluid 1135 pressure on'oneend of said plunger.

5. In a piston, the combination of a supporting body which is providedwith an, upper concave annular surface, said bodyhaving an outercylindrical surface and having an axial bore extending into said body, aplunger slidably mounted in said axial bore and carrying at its end acircular member having a lower convex annular surface, and a pluralityof packings comprising flexible impermeable members, each provided with'a pair of frusto-conical flanges, said flanges of each packing beingjoined together along the line of a circle to form a substantiallyV-shaped member having'be-veled edges, the outer edges of said packingsbeing adapted to engage the 15C walls of a cylinder, and the inner wallsof packings engaging said plunger, said circular member initiallyengaging the packings adjacent, their outer edges inside the V-shapedmembers,

said

and said lower concave annular surface initially engaging the apex ofsaid packing assembly, whereby 'said packings are expanded into engagement with the walls of a cylinder and with said plunger by pressureinside the cylinder.

-6. In a piston, the combination of a supporting body which is providedwith an upper concave annular surface, said body having an outercylindrical surface and having an axial bore extending intosaid body, aplunger slidably mounted in said axial bore and carrying at its end acircular member having a lower convex annular surface, and a pluralityof packings comprising flexible impermeable members, each provided witha pair of frust'o-conical flanges, said flanges of each packing beingjoined together along'the line of a circle to form a substantiallyV-shaped memberhaving beveled edges, the outer edges of said packingsbeing adapted to engage the walls of 'a cylinder, and the inner walls ofsaid Epackings engaging said plunger, said circular member initiallyengaging the packings adjacent their outer edges inside the V-shapedmembers, and said lower concave annular surface initially engaging theapex 'of said packing assembly, whereby said packings are expanded-intoengagement with the walls of a cylinder and with said plunger bypressure inside the cylinder, said circular member having a plurality ofapertures providing an access into the interior of the cylinder and theinterior of the V-shaped packing assembly 'to utilize the effect offluid pressure on the packing.

'7. In a piston, the combination of a supporting body which is providedwith an upper concave :annular surface, said body having an outercylindrical surface and having an axial bore extending into said body, aplunger slidably mounted in said axial bore and carrying at its end acircular member having a lower convex annular surface, and a pluralityof packings comprising flexible impermeable members, each provided witha pair of frusto-cenical flanges, said flanges of each packingbeingjoined together along the line of a circle to form a substantiallyV-shaped member having beveled edges, the outer edges of said packingsbeing adapted to engage the walls of a cylinder, and the inner walls ofsaid'packings engaging said plunger, said circularmember initiallyengaging the packings adjacent their outer edges inside the V-shapedmembers, and said lower concave annular surface initially engaging theapex of said packing assembly, whereby said packings are expanded intoengagement with the walls of a cylinder and with said plunger ,bypressure inside thecylinder, and resilient disposed at one end, with acircular member mounted on a plunger in said piston projecting throughand sliding with respect to said packings to cause said annular memberto engage the pressure side of said packings, and means for releasingthe pressure caused by leakage of fluid past said packings about saidplunger to prevent fluid pressure from building 'up on the side of saidpackings opposite from the pressure cham ber of said cylinder.

9. In a piston, the combination of a supporting body which is providedwith an' upper concave annular surface, said body having an outercylindrical surface and having an axial bore extending into said body, aplunger slidably mounted in said axial bore and carrying at its end acircular member having a lower convex annular surface, and a pluralityof packings comprising flexible impermeable members, each provided witha pair of frusto-conical flanges, said flanges of each packing beingjoined together along the line of a circle to form asubstantially'V-shaped member having beveled edges, the outer edges ofsaid packings being adapted to engage the walls of a cylinder, and theinner walls of said packings of the V-shaped packing assembly to utilizethe effect of fluid pressure on the packing, one of said packingscomprising a felt member of simiengaging said plunger, said circularmember inilar V shape impregnated with solid lubricating material tomaintain the lubrication of said packings. CHARLES W. MARSH.

